Turbopropeller or turboshaft gas turbine engines suffer from a loss of power due to erosion of the gas generator compressor by dust, debris, or other foreign bodies. This is due to dust, debris or other foreign bodies lying on the ground or airport runway being entrained into the air entering the gas turbine engine intake duct, or ducts. The erosion is very severe when a turbopropeller gas turbine engine is in the reverse thrust mode, erosion also occurs when there is zero forward speed and zero net thrust.
Turbopropeller or turboshaft gas turbine engines have been protected from foreign bodies by providing separating ducts which remove the foreign bodies. These separating ducts have ejectors driven by hot gases from a turbine to induce a flow in the separating duct, and some have ejectors which extend into the center of the duct to provide complete mixing.
However it is undesirable to use hot gases as it is difficult to control the flow of hot gases to the ejectors, and leakage of hot gases into the intake duct is not desirable. The positioning of the ejector in the center of the separating duct prevents the passage of large foreign bodies through the separating duct, and the ejector can be damaged by the passage of the large foreign bodies through the separating duct.